Linear amplifiers have proven difficult to achieve using metal oxide semiconductor (MOS) devices. However, the MOS approach to integrated circuit (IC) construction has proven to be so effective that it has become one of the dominant construction forms. Since it would be desirable to incorporate linear amplifiers into MOS IC devices, many circuit approaches have been tried. The most common approach to differential amplifier design uses a circuit configuration very similar to the long-tailed pair construction well known in the bipolar transistor art. In the MOS version a pair of enhancement transistors are coupled to a pair of depletion load devices from which the output is derived. The enhancement transistors are differentially driven from the input and their sources are coupled to a common tail current source. In such a circuit the common mode range is restricted and the power supply potential must exceed two thresholds.